Gas pipeline by pipe process can be divided into seamless steel pipe (SMLS), ERW steel pipe SSW steel pipe ,LSAW steel pipe ,HFW steel pipe etc...
Mainly as a field gathering pipe and internal high-pressure natural gas pipeline of small-caliber, long-distance pipelines for oil and gas a small number, the vast majority of long-distance pipeline is the use of high-frequency straight seam welded pipe (ERW), spiral submerged arc welded pipe (SSAW), LSAW steel pipe (LSAW) three.
The following table shows the characteristics of several steel process and quality performance comparison:
Straight seam high frequency welded pipe (ERW steel pipe) by welding and induction welding is divided into different exposure to welding in two forms, using broadband hot-rolled coils as raw materials, pre-curved, continuous molding, welding, heat treatment, sizing, straightening, cutting and other processes, and spiral welded pipe weld compared to the short, high dimensional accuracy, uniform thickness, surface quality, the advantages of higher pressure, but the drawback is that only produce small-caliber thin-walled tube, easy to produce weldsgray leaf spot, not fusion, groove-shaped corrosion defects. At present more extensive application areas of the city gas, crude oil transportation and so on.
Straight seam high frequency welded pipe (ERW steel pipe) by welding and induction welding is divided into different exposure to welding in two forms, using broadband hot-rolled coils as raw materials, pre-curved, continuous molding, welding, heat treatment, sizing, straightening, cutting and other processes, and spiral welded pipe weld compared to the short, high dimensional accuracy, uniform thickness, surface quality, the advantages of higher pressure, but the drawback is that only produce small-caliber thin-walled tube, easy to produce weldsgray leaf spot, not fusion, groove-shaped corrosion defects. At present more extensive application areas of the city gas, crude oil transportation and so on.
Spiral submerged arc welded pipe (SSAW steel pipe) is the strip volume control when the forward direction and forming a molding pipe centerline angle (adjustable), side molding edge welding, the weld into a spiral, the advantage of the same specifications of the strip can beproduction of a variety of diameters of pipe, meet a wider range of raw materials, welds can avoid the main stress, the force is better, the disadvantage is poor geometry,the weld seam length compared to the straight pipe length, easy to produce cracks, pores, slag, welding and other welding defects side, welding stress was tensile stress state.General long-distance gas pipeline design specification spiral submerged arc welded pipe can only be used for Class 3, Class 4 area.
Foreign raw materials will be changed to improve this process steel, so that separate forming and welding, the welding and lean pre-, post-weld cold-expanding, then the quality of welding close to the UOE pipe, currently there is no such process,is the spiralFactory directions for improvement. "Natural Gas" is still used by the traditional spiral process of production, but the tube side of the expander.United States, Japan and Germany in general negative SSAW, that trunk should not use SSAW; Canada and Italy, some use SSAW, Russia, a small amount of use SSAW, and have developed a very strict additional conditions, due to historical reasons, most still use the main trunk domestic SSAW. LSAW pipe (LSAW) is a single plate as raw material, steel in the mold or molding machine pressure (volume) into the tube, using double-sided submerged arc welding method and Expanding from the produce.
The wide range of product specifications, weld toughness, ductility, good uniformity and dense, with a large diameter, wall thickness, high pressure, low temperature corrosion resistance and other advantages.
In the construction of high-strength, high toughness, high-quality long-distance gas pipeline, most of the required large diameter thick wall steel pipe LSAW pipe.According to API standards, in large oil and gas pipelines, when through the alpine zone, sea, cities and other densely populated areas Class 1, Class 2 areas, LSAW pipe is the only designated suitable tube.By forming different ways can be divided into:
- UOE welded pipe: sheet steel at the edge of the pre-bend, the U shape, O shape, welded inside and outside welding, mechanical cold Expanding processes;
- JCOE pipe: ie "JCOE" pre-welding, forming, welding and other processes by the cold expander;
- HME pipe: the mandrel rolling basis over the "CCO" forming, welding and other processes by the cold expander.
